surface structure 
noun [mass noun]
(In transformational grammar) the structure of a well-formed phrase or sentence in a language, as opposed to its underlying logical form: rules of transformation change deep structure into surface structure [count noun]: those types of sentences which have deep structures identical to their surface structures will be called base sentences...Contrasted with deep structure.
- Possibly, the present verbal dual task interferes mostly with the phonological surface structure of the spatial sentence and not with the underlying propositional content.
- That is, switching should occur at points where the surface structures of the two languages map onto each other.
- The theory postulates that the two sentences have the same order in deep structure, but the question transformation changes the order to that in surface structure.